# OS_EnableIrqMask

## C Specification

      #include <nitro/os.h>

      OSIrqMask OS_EnableIrqMask( OSIrqMask intr );

## Description

This function sets the IRQ interrupt cause. In addition to the current setting, the designated cause's enable bit is enabled. Refer to `OS_SetIrqMask`.

Note:

Adds the specified causes in addition to the current settings

`OS_SetIrqMask` is used to overwrite and set a specific cause. However, since there may be interrupt cause settings defined by the system which we do not wish to change, there may not be a situation in which a user will overwrites and sets a specific cause using the `OS_SetIrqMask` function. In such cases, the `OS_EnableIrqMask` function should be used to set the specific cause.

## Internal Operation

Operates one IO register, the IE (Interrupt Enable) register.

## Arguments

`intr` | The IRQ interrupt cause to be enabled (expressed as a logical sum)

## Return Value

The IRQ interrupt cause that was set before this function is called.

## See Also

`OS_DisableIrqMask`, `OS_SetIrqMask`

## Revision History

03/12/2004 Emphasized the difference from `OS_SetIrqMask`
12/01/2003 Initial version